Diverse response of surface ozone to COVID-19 lockdown in China

Yiming Liu; Tao Wang; Trissevgeni Stavrakou; Nellie Elguindi; Thierno Doumbia; Claire Granier; Idir Bouarar; Benjamin Gaubert; Guy P Brasseur

doi:10.1016/j.scitotenv.2021.147739

Diverse response of surface ozone to COVID-19 lockdown in China

Sci Total Environ. 2021 Oct 1:789:147739. doi: 10.1016/j.scitotenv.2021.147739. Epub 2021 May 15.

Authors

Yiming Liu¹, Tao Wang², Trissevgeni Stavrakou³, Nellie Elguindi⁴, Thierno Doumbia⁴, Claire Granier⁵, Idir Bouarar⁶, Benjamin Gaubert⁷, Guy P Brasseur⁸

Affiliations

¹ Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong, China. Electronic address: liuym88@mail.sysu.edu.cn.
² Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong, China. Electronic address: cetwang@polyu.edu.hk.
³ Royal Belgian Institute for Space Aeronomy, Brussels, Belgium.
⁴ Laboratoire d'Aérologie, Toulouse, France.
⁵ Laboratoire d'Aérologie, Toulouse, France; NOAA Chemical Sciences Laboratory and CIRES, University of Colorado, Boulder, CO, USA.
⁶ Environmental Modeling Group, Max Planck Institute for Meteorology, Hamburg, Germany.
⁷ Atmospheric Chemistry Observations and Modeling Laboratory, National Center for Atmospheric Research, Boulder, CO, USA.
⁸ Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong, China; Environmental Modeling Group, Max Planck Institute for Meteorology, Hamburg, Germany; Atmospheric Chemistry Observations and Modeling Laboratory, National Center for Atmospheric Research, Boulder, CO, USA.

Abstract

Ozone (O₃) is a key oxidant and pollutant in the lower atmosphere. Significant increases in surface O₃ have been reported in many cities during the COVID-19 lockdown. Here we conduct comprehensive observation and modeling analyses of surface O₃ across China for periods before and during the lockdown. We find that daytime O₃ decreased in the subtropical south, in contrast to increases in most other regions. Meteorological changes and emission reductions both contributed to the O₃ changes, with a larger impact from the former especially in central China. The plunge in nitrogen oxide (NO_x) emission contributed to O₃ increases in populated regions, whereas the reduction in volatile organic compounds (VOC) contributed to O₃ decreases across the country. Due to a decreasing level of NO_x saturation from north to south, the emission reduction in NO_x (46%) and VOC (32%) contributed to net O₃ increases in north China; the opposite effects of NO_x decrease (49%) and VOC decrease (24%) balanced out in central China, whereas the comparable decreases (45-55%) in these two precursors contributed to net O₃ declines in south China. Our study highlights the complex dependence of O₃ on its precursors and the importance of meteorology in the short-term O₃ variability.

Keywords: COVID-19; Emission reduction; Meteorological condition; Surface ozone.